Testing and conselling increases condom use in HIV-discordant couples, but unsafe sex under-reported

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Voluntary HIV testing and counselling was associated with a substantial increase in self-reported condom use amongst HIV-discordant heterosexual couples in a study conducted by the University of Alabama and University of Zambia in Lusaka Zambia. However, the study, which is published in the 28th March 2003 edition of AIDS, also showed that biological markers were able to detect widespread under-reporting of unprotected sex.

Between 1994 and 1998 investigators enrolled 983 HIV-discordant couples who had received voluntary HIV testing and counselling. Investigators wished to establish condom use before and after HIV testing and counselling, patterns of self-reported condom use after testing and counselling and the validity of self-reported condom use was checked using biological markers. Sexual behaviour and condom use amongst the HIV-discordant couples was compared to a control population of HIV-negative couples.

To be included in the study couples had to be living together for at least six months. Women were required to be under 48 years of age and men under 65. Attendance at at least one follow-up visit was also required.



A serodiscordant couple is one in which one partner has HIV and the other has not. Many people dislike this word as it implies disagreement or conflict. Alternative terms include mixed status, magnetic or serodifferent.


A sexually transmitted infection caused by the bacterium Treponema pallidum. Transmission can occur by direct contact with a syphilis sore during vaginal, anal, or oral sex. Sores may be found around the penis, vagina, or anus, or in the rectum, on the lips, or in the mouth, but syphilis is often asymptomatic. It can spread from an infected mother to her unborn baby.

loss to follow up

In a research study, participants who drop out before the end of the study. In routine clinical care, patients who do not attend medical appointments and who cannot be contacted.

deoxyribonucleic acid (DNA)

The material in the nucleus of a cell where genetic information is stored.

Study participants were invited back every three months when they were interviewed separately. Questions about condom use and sex outside the relationship were asked. The HIV-negative partner was tested for HIV and both partners were screened for gonorrhoea and syphilis. Women also had a vaginal swab to check for sperm and T. vaginalis.

Before voluntary HIV testing and counselling condom use was reported by under 3% of the discordant couples in the study. However, this increased to over 80% after testing and counselling and remained stable at this level through over twelve months of follow-up. Condom use amongst the HIV-negative couples was reported for only 28% of sexual episodes.

Couples who regularly attended appointments through twelve months were more likely to report to report frequent condom use than couples who either missed appointments or were lost to follow-up. Regular attendance was also associated with fewer unprotected contacts. Amongst the regular attenders, 99% reported having had sex with a condom on at least one study visit, with 56% reporting condom use at all four visits.

However, biological markers suggested that there was significant under-reporting of sex without condoms. In total 25% of vaginal smears showed semen, suggesting unprotected sex within the last four days, and sperm was detected in 15% of smears even though partners reported 100% condom use.

Nevertheless, consistently reported condom use was associated with a 70% reduction in the incidence of pregnancy and 52% reduction in linked HIV transmission. Furthermore, sperm detection amongst HIV discordant couples was 47% lower than amongst concordant HIV-negative couples.

Sex outside the study relationship was reported by 21% of HIV-positive men and 15% of HIV-negative men in discordant relationships. Women reported a much lower frequency of sex outside their relationship, amounting to only 0.3% of all sexual acts.

Rates of sexually transmitted infections were assumed by the investigators to reflect sexual contact outside the relationship. Rates were low, with gonorrhoea detected in 6.1% of men reporting sex outside their relationship and 2.3% reporting monogamy. The incidence was syphilis was lower still. T. vaginalis was detected in 10.7% of women reporting outside contacts and a little over 7% of women without.

One hundred and seven HIV seroconversions took place during the course of the study. It was possible to carry out DNA sequencing in 94 of these seroconverters and 87% of infections were found to have come from within the relationship.

"In this study, Zambian discordant couples reported a marked increase in condom use after voluntary testing and counselling and maintained this risk reduction for at least a year", note the investigators. However, sperm and sexually transmitted infections indicated that at least 50% of unprotected sex went unreported.

The investigators further note that although couples with HIV-positive men reported less frequent sex, "They were more likely to report 100% condom use. This confirms that in areas where women often have difficulty negotiating condom use, many men who know that they have HIV willingly use condoms to protect their uninfected spouses."

Voluntary testing and counselling should be a top priority for HIV prevention programmes conclude the authors, but more is needed to improve the validly of self-reported risk reduction.

Further information on this website

HIV antibody test - Menu of information

Condoms - Factsheet

Unprotected sex - Factsheet


Allen S et al. Sexual behaviour of HIV discordant couples after HIV counseling and testing. AIDS 17:733-40, 2003.